Monitoring online queries can provide early and accurate information about the spread of COVID-19 in the population and about the effectiveness of COVID-19 epidemic control measures.
The purpose of the study. Assessment of significance of online queries regarding smell impairment to evaluate the epidemiological status and effectiveness of COVID-19 epidemic control measures.
Materials and methods. Weekly online queries from Yandex Russian users regarding smell impairment were analysed in regions and large cities of Russia from 16/3/2020 to 21/2/2021. A total of 81 regions of Russia and several large cities, such as Moscow, St. Petersburg, and Nizhny Novgorod, were included in the study.
Results. A strong positive direct correlation (r>0.7) was found between the number of smell-related queries in Yandex new cases of COVID-19 in 59 out of 85 Russian regions and large cities (70%). During the "first" peak of COVID-19 incidence in Russia (April-May 2020), the increase in the number of smell-related queries outpaced the increase in the number of new cases by 1-2 weeks in 23 out of 59 regions of Russia. During the "second" peak of COVID-19 incidence in Russia (October-December 2020), the increase in the number of smell-related queries outpaced the increase in the number of new cases by 1-2 weeks in 36 regions of Russia, including Moscow. We also estimated the increase in the query/new case ratio during the "second" peak of incidence for 45 regions. It was found that the query/new case ratio increased by more than 100% in 24 regions. The regions where the increase in queries was more than 160% compared to new infection cases during the "second" peak of incidence demonstrated significantly higher search activity related to levofloxacin than the regions where the increase in queries was lower than 160% compared to the increase in new infection cases.
Conclusion. The sudden interest in smell impairment and growing frequency of online queries among the population can be used as an indicator of the spread of coronavirus infection among the population as well as for evaluation of the effectiveness of COVID-19 epidemic control measures.
Keywords: COVID-19, SARS-CoV-2 coronavirus, Yandex.Wordstat, correlation, query, sense of smell.